Implantable medical devices are available for monitoring physiological signals of a patient. Physiological signals may be analyzed by the device for automatically detecting an adverse physiological condition or event. The physiological monitoring may be used by the device for controlling automatic delivery of a therapy, such as an electrical stimulation therapy or a drug therapy. The medical device may be provided with a patient alarm for notifying the patient of the presence of the detected physiological event or condition. The patient may then take appropriate action, such as seeking medical attention, as previously advised by a clinician. Typically a threshold value is defined, which when crossed by a monitored physiological parameter triggers the patient alarm. The threshold for triggering an alarm may be set to a nominal value or a value derived from clinical data relating to a selected patient population. The threshold may not be individualized for a particular patient, potentially resulting in the triggering of false alarms. Such false alarms are inconvenient both to the patient and the treating physician. Accordingly, a method and apparatus are needed for setting an appropriate threshold for individual patients for detecting a physiological condition and triggering a patient alarm.